Process of coating tablets with alternate tacky and non-tacky layers



United States Patent 3,524,756 PROCESS OF COATING TABLETS WITH ALTER-NATE TACKY AND NON-TACKY LAYERS Charles A. Signorino, King of Prussia,and Thomas E.

Jamison, Philadelphia, Pa., assignors to 'Colorcon Incorporated, WestPoint, Pa., a corporation of Pennsylvania No Drawing. Filed May 29,1967, Ser. No. 642,190 Int. Cl. B44d 1/14 US. Cl. 117-72 13 ClaimsABSTRACT OF THE DISCLOSURE Process of coating tablets with alternatelayers of liquid suspension of tacky material and aqueous suspension ofnon-tacky material wherein the tacky material is shellac, zein or gumarabic and the non-tacky material is sugar.

BACKGROUND OF THE INVENTION One of the most important problems in thepharmaceutical industry has been the preparation of dosage forms whichare safe and do not disintegrate or change while on the shelf, and"which disintegrate as planned in the stomach or intestines when taken bythe patient. Among the most popular and useful dosage forms beingprepared today are coated tablets.

Tablets are commonly coated with a layer of sugar, but even when thesugar solution contains opaque color pigments, the compressed tabletcore requires sub-coating with sucrose and dusting powders to get arounded form. The tablet core also requires a coating or layer ofsealant to protect the core against moisture.

Compressed tablet cores may be sealed against moisture by coating themdirectly with a film such as with methyl cellulose. However, such directfilm coating requires elaborate spray and exhaust systems. This is trueof most of the useful synthetic polymers, since they are not adapted tocoating by ladling into a coating pan containing the tablet cores andthen rotating the pan.

Shellac is widely used as a sealing coating on tablet cores, and also asa finish coating, if it does not matter that the tablets have a mottledor uneven appearance. Shellac has the advantages of being an excellentmoisture barrier, and of being adaptable to being applied to the tabletcores by ladling onto the tablet cores in a rotatable coating pan.

However, shellac has several disadvantages. The shellac coats after thefirst one do not distribute color Well. Moreover, the shellac film isnot smooth because the subsequent layers of shellac activate thosealready deposited and cause a picking between tablets that transfers theshellacfrom one tablet to another and gives an orange peel effect and ageneral uneveness in color as well as pin holes in the film layer.

Another disadvantage of shellac coatings on tablets is the tendency ofthe shellac to polymerize upon standing on the shelf. This causes thedisintegration time of the tablet to be extended so that the tablet maynot disintegrate in the stomach as intended, or in the intestines, butmay pass through the body without disintegrating at all.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide a process for coating tablets with film so as to seal thetablet core against moisture and to overcome the problems of tackiness,mottling, uneveness of film coating and color, disintegration or changein characteristics while the tablets are on the shelf, and failure ofthe tablets to disintegrate in the body.

3,524,756 Patented Aug. 18., 1970 DESCRIPTION OF THE PREFERREDEMBODIMENTS The process of the invention permits ladling an anhydroussuspension, such as a shellac suspension, directly on tablet coresrolling in a coating pan.

In accordance with the process, compressed tablet cores are screened toremove dust, and are deposited in a rotatable coating pan. A sufiicientquantity of a shellac color suspension is applied to thoroughly wet thetumbling tablet cores. After the suspension is uniformly distributedabout the cores for about 1 minute, Warm air is applied to the tabletswhile they are still rolling until the tablet cores start to break loosefrom each other and become less tacky. The Warm air is applied to therolling tablets for about 4 minutes. Then the pan is stopped and isintermittently jogged every minute for about 10 minutes. The joggingcomprises rotating the coating pan for /z revolution so as not to letthe coated cores sit in the pan and adhere to each other.

After about 10 minutes of this jogging, this first coating issufficiently dry to take a second coating. This second coating may beanother coating, one-half the volume, of the shellac suspension if adouble sealing layer of shellac is desired. The second shellac layer ismore tacky than the first shellac layer, but this tackiness is not aserious problem.

Instead of applying a second coating of shellac immediately, it ispreferred to apply sugar syrup as the second coating. The sugar coatingmay be applied by ladling plain sugar syrup into the coating pan ontothe tablet cores and rolling the sugar layer dry in about 5 minutes.

Instead of plain sugar syrup, a sugar suspension of 10 to 25 pound cut,preferably a 16-22 pound cut, of sucrose syrup is formed into a sugarsuspension by add ing 1 to 5 percent by weight of a shellac suspension.By 10 to 25 pound cut sucrose syrup is meant 10 to 25 pounds of sugardissolved in one gallon of water. This sugar suspension containing thesmall amount of shellac suspension has the advantage of etching orsoftening the previous shellac layer slightly to form a better or moresecure bond of the sugar coating to the shellac coating. Since theshellac suspension is colored, its addition to the sugar suspensiongives color to the sugar suspension and therefore the sugar coating aidsin adding color instead of just forming a colorless base for the nextcolor application.

The sugar suspension aids in developing the color of the tablet morerapidly. The sugar layer adheres well to the first layer of shellac andprovides a fiat, non-tacky surface for a third coating layer which maybe of shellac.

After the sugar is dried in the second coating layer, a layer of shellacis applied to form the third coating layer. This third layer is appliedby ladling a sufiicient amount of shellac suspension onto the tabletcores to wet them completely, then rolling the tablet cores until theybreak free from each other, then jogging the coating pan every minutefor about 10 minutes to dry the tablet cores.

This procedure of applying alternate coating layers of shellac and sugarmay be continued until the desired full color of the tablet is achieved.

Advantageously, the anhydrous suspension may comprise a shellac coatingsuspension including, by weight,

30 parts of 4 pound cut shellac (4 pounds of shellac dissolved in agallon of alcohol), 3 parts of slip and levelling agents, 25 parts ofpigment solids, and ethyl alcohol, denatured. Also, the shellacsuspension may include 2 parts of polyvinyl-pyrrolidone. The slip andlevelling agents may be in the range of about -6 parts, the pigmentsolids -30 parts, and the olyvinylpyrrolidone 0-5 parts.

The slip agents are included in the shellac suspension in order tochemically reduce the tacking of the shellac so that the tablet coresslip by instead of picking. The slip agents may include cetyl alcohol,glycol monostearate, and talc.

The levelling agents are included in order to help spread the shellacsuspension evenly over the tablet cores. The levelling agents mayinclude sorbitan monooleate, and sorbitan monostearate. Acetylatedmonoglyceride may be included in the shellac coating suspension as botha levelling and a slip agent.

The olyvinylpyrrolidone is included in the shellac suspension to reducethe tendency of the shellac to polymerize and to modify the shellac filmto help stabilize it.

The pigment solids may include all the FD & C and D & C lakes, solubleand insoluble dyes, opacifiers, titanium dioxide, calcium carbonate,silica, iron oxides and channel black formulated to desired color.

For example, to obtain a tablet having a dark cherry red color, thepigment solids include FD & C Red No. 3, FD & C Violet No. 1, talc andtitanium dioxide.

The alcohol may be a specially denatured alcohol such as 3A ethylalcohol, denatured, and it is used in suflicient quantity to give aviscosity of the shellac suspension of to seconds in a No. 3 Zahn cup at25 C.

The sugar syrup may comprise, by weight, 14 parts of sucrose, and 6parts of water. If desired, 1 part of the shellac suspension may beadded to the sugar syrup to produce the sugar suspension.

In practicing the process of the invention, 14 pounds of 3 grain scoredplacebos are loaded into a 16 inch spherical coating pan. Then 175milliliters of the shellac suspension are ladled over the rolling tabletcores and after the suspension is thoroughly distributed, air at 100 F.is directed onto the tablet cores to dry them to the extent that theyseparate from each other. Then the coating pan is jogged for revolutionevery minute for about 10 minutes while still directing the air onto thetablets to further dry the tablets.

If a second sealing coat is necessary before the aqueous coating can beapplied, then 60 milliliters of the shellac suspension may 'be dilutedwith 20 milliliters of 3A ethyl alcohol and ladled onto the tablets inthe coating pan. This diluted shellac suspension may be used so as notto get too much shellac on the tablet core, and to spread the dilutedshellac suspension uniformly over all the tablets since the dilutedsuspension is thinner and easier flowing.

Next, milliliters of the sugar suspension is added and is allowed todistribute evenly and is dried with air in about 4 minutes. This stepcan follow the first shellac coating directly if a good first coat isapplied or the cores are not excessively sensitive to moisture.

Then 80 milliliters of the shellac suspension diluted by alcohol in theratio of 3 parts of the shellac suspension to 1 part of alcohol is addedand forms a coating over the sugar coating. This shellac coating isdried with air. A good fiat, non-tacky, uniform layer of colored shellacis obtained and this may complete the tablet coating if desired.

If additional coating is desired, after about 12 minutes, 45 millilitersof the sugar suspension is added and is dried with cool air. Then 80milliliters of the 3 to 1 diluted shellac suspension is added and thetablets are rolled dry with air without picking. A good uniform film ofshellac and color is observed on the tablets.

Then 15 milliliters of the shellac suspension diluted with 15milliliters of alcohol are added after about 10 minutes to get a morecomplete shellac finishing layer and to get a polished finish ratherthan a flat coating on the outside of the tablet. A very thin film isobtained so as to avoid any picking between tablets.

After standing 20 days, such coated tablets disintegrate in 5 minutes insimulated gastric fluid. After six months in storage the disintegrationtime was still 5 minutes in simulated gastric fluid.

To further illustrate the invention, the following examples of specificshellac suspensions will make obvious to one skilled in the art thepractice of the invention.

. Example 1 Ingredients: Amounts 4 pound cut bleached shellac 11 pounds,14 ounces.

Cetyl alchol 3 /1 ounces. Isopropyl alcohol 4 pounds, 2 /2 ounces.Sorbitan monooleate 5 ounces. Sorbitan trioleate 5 ounces. FD & YellowNo. 5 Lake 2 pounds, 13 ounces. FD & Blue No. 1 Lake 15% ounces.Titanium dioxide 9 pounds, 9 ounces. Talc 2 pounds, 8 /2 ounces.Polyvinylpyrrolidone 3 ounces,

The tablets are coated by alternately applying a layer of a shellacsuspension. and a layer of sugar suspension to the tablet cores, dryingone layer before applying the next layer. The suspensions are applied byladling them onto the tablet cores being rotated in a coating pan, andthis procedure is repeated as often as necessary to obtain the desiredcoloring and depth of film coating.

Example 2 Ingredients: Amounts 4 pound cut bleached shellac 11 pounds,14 ounces.

Cetyl alchol 3 /2 ounces. Isopropyl alcohol 5 pounds, 6 /2 ounces.Sorbitan monooleate 5 ounces. Sorbitan trioleate 5 ounces. FD & C YellowNo. 5 Lake 2 pounds, 15% ounces. Titanium dioxide 1 pound, 2 /2 ounces.Talc 1 pound, 13% ounces. Polyvinylpyrrolidone 7 /2 ounces.

The shellac suspension of Example 2 is applied to the tablet cores inthe same manner as previously described. Other examples of specificshellac suspensions are as follows.

Example 3 Ingredients: Amounts 4 pound cut bleached shellac 4 pounds, 6%ounces. Cetyl alcohol 1% ounces. Isopropyl alcohol 1 pound, 4 ounce.Sorbitan monooleate 2 ounces. Sorbitan trioleate 2 ounces. Titaniumdioxide 1 pound. FD & C Red No. 2 Lake 6 ounces. Talc 10 ounces.Polyvinylpyrrolidone 4 ounces.

Example 4 Ingredients: Amounts 4 pound cut unbleached shellac 5 pounds,12 ounces.

Sorbitan monooleate 6% ounces. Acetylated monoglyceride ounce.Polyvinylpyrrolidone 4 /2 ounces. FD & C Violet No. 1 Lake 12 /2 ounces.Titanium dioxide 1 pound, 10 /2 ounces. Talc 10 ounces.

Ethyl alcohol, denatured 1 pound.

In practicing this invention, the tacky substance which forms a coatinglayer on the tablet cores may be shellac or other natural polymericmaterials of similar properties such as zein, or gum arabic. Thenon-tacky substance may be sucrose or other sugars that dry under normalcoating procedures.

The word tablets as used herein includes any discrete solids such aspellets, pills, candy, and other forms.

The advantages of the invention are numerous. The sugar coating layerprovides a good flat non-tacky base for the uniform spreading of ashellac layer which is applied thereto. The flat non-tacky finish of thesugar layer lessens the incidence of tablet-to-tablet picking, therebyavoiding the orange peel effect of uneven color distribution. Also, thesugar coatings aid in disintegrating the film coatings of the tabletafter the tablet has been swallowed by a patient.

The color development of the tablet cores coated in accordance with theinvention is more rapid and mottle free than conventional tabletsbecause the shellac films or layers build up uniformly without beingredistributed through picking. Without the intervening sugar layers, theshellac layers would build unevenly because of picking between tablets.

Also, the use of sugar coating layers between applications of theshellac suspension makes the coating operation much more simple. Theattention of the coating operator is not as critical since dusting isunnecessary, and each new application of shellac goes on the tablet corewith the ease of the first application.

What is claimed is:

1. A process of coating tablets comprising applying a liquid suspensionto the tablets to form a first tacky layer, drying the first tackylayer, applying an aqueous suspension of sugar to the dried tacky layerto form a non-tacky layer, drying the non-tacky layer, applying saidliquid suspension to the dried non-tacky layer to form a second tackylayer, and drying the second tacky layer, said tacky layers consistingessentially of shellac, zein, or gum arabic.

2. The process of claim 1 wherein, in parts by weight, the shellacsuspension comprises about 30 parts of 4 pound cut unbleached shellac, 3parts of slip and levelling agents, 25 parts of pigment solids, and asufiicient quantity of ethyl alcohol, denatured, to give a viscosity ofthe shellac suspension of 15-30 seconds in a No. 3 Zahn cup at 25 C.,and the sugar suspension comprises 14 parts of sucrose and 6 parts ofwater.

3. The process of claim 2 wherein the shellac suspen sion also includesabout 2 parts of polyvinylpyrrolidone.

4. The process of claim 2 wherein the sugar suspension also includes 1part of said shellac suspension for each 20 parts of sucrose and water.

5. The process of claim 1 wherein the shellac suspension includes thefollowing ingredients in the following ratios by weight: 5 pounds 12ounces of 4 pound cut unbleached shellac, 6 /8 ounces sorbitanmonooleate, ounce acetylated monoglyceride, 4 /2 ounces ofpolyvinylpyrrolidone, 12%. ounces FD & C Violet No. 1 Lake, 1 pound 10/2 ounces titanium dioxide, 10 ounces of talc, and 1 pound of ethylalcohol, denatured.

6. The process of claim 1 wherein the shellac suspension includes thefollowing ingredients in the following ratios by weight: 11 pounds 14ounces of 4 pound cut bleached shellac, 3 /2 ounces cetyl alcohol, 4pounds 2 /2 ounces isopropyl alcohol, 5 ounces sorbitan monooleate,

6 5 ounces sorbitan trioleate, 2 pounds 13 ounces FD & C Yellow No. 5Lake, 15% ounces FD & C Blue No. 1 Lake, 9 pounds 9 ounces titaniumdioxide, 2 pounds 8 /2 ounces talc, and 3 ounces polyvinylpyrrolidone.

7. The process of claim 1 wherein the shellac suspension includes thefollowing ingredients in the following ratios by weight: 11 pounds 14ouces of 4 pound cut bleached shellac, 3 ounces cetyl alcohol, 5 pounds6 /2 ounces isopropyl alcohol, 5 ounces sorbitan monooleate, 5 ouncessorbitan trioleate, 2 pounds 15% ounces FD & C Yellow No. 5 Lake, 1pound 2 /2 ounces titanium dioxide, 1 pound 13% ounces talc, and 7 /2ounces polyvinylpyrrolidone.

8. The process of claim 1 wherein the shellac suspension includes thefollowing ingredients in the following ratios by weight: 4 pounds 6ounces of 4 pound cut bleached shellac, 1% ounces cetyl alcohol, 1 poundounce isopropyl alcohol, 2 ounces sorbitan monooleate, 2 ounces sorbitantrioleate, 1 pound FD & C Red No. 2 Lake, 6 ounces titanium dioxide, 10ounces talc, and 4 ounces polyvinylpyrrolidone.

9. The process of claim 1 wherein the shellac is colored with a coloringagent.

10. The process of claim 9 wherein the coloring agent is FD & C and D &C lakes, soluble and insoluble dyes, iron oxides, channel black oropacifiers.

11. A method of coating tablet cores comprising forming a suspension ofliquid non-aqueous material, forming a suspension of aqueous material,rolling the tablet cores in a coating pan, ladling the liquidnon-aqueous suspension onto the rolling tablet cores to form a firstcoating layer, drying the coating layer, ladling the aqueous suspensiononto the rolling cores to form a second coating layer, drying the secondcoating layer, ladling the liquid non-aqueous suspension onto therolling cores to form a third coating layer, and drying the thirdcoating layer, said liquid non-aqueous material consisting essentiallyof shellac, zein, or gum arabic, said aqueous suspension consistingessentially of sugar.

12. The method of claim 11 wherein the tablet cores are screened toremove dust before being rolled in the coating pan.

13. The method of claim 11 wherein warm air is applied to the rollingtablet cores being coated with the first coating layer for about 4minutes until the cores break loose from each other, and then the pan isjogged intermittently for about 10 minutes until the first coating layeris dry.

References Cited UNITED STATES PATENTS 2,865,810 12/1958 Sanders 1l7--12X 2,881,085 4/ 1959 Endicott et al.

2,982,234 5/1961 Ackley et al. 11712 X 3,097,144 7/1963 Banker l1772 X3,159,544 12/1964 Heffernan et al. 117-12 X 3,383,236 5/1968 Brindamour.

3,420,931 l/l969 Davm et al. 11772 X 3,427,182 2/ 1969 Zingerman 11772WILLIAM D. MARTIN, Primary Examiner R. HUSACK, Assistant Examiner US.Cl. X.R.

